1. Field of the Invention
The present invention relates to a resonance sound adding apparatus for a keyboard instrument.
2. Description of the Related Art
In an acoustic piano, a string which is struck by a hammer of a keyboard resonates with a string of another tone in a state in which a damper pedal is pressed and damping of strings is released. By way of example, an electronic piano has functions of generating a resonance sound which imitates a resonant state between strings of the acoustic piano, adding the generated resonance sound to the sound having a pitch of a pressed key, and outputting resulting sound.
Jpn. Pat. Appln. KOKAI Publication No. 06-149245 discloses an apparatus that, in response to pressing of a damper pedal, changes an envelope for direct sound and an envelope for resonance sound, and changes sound volume. The envelope for the direct sound is attached to a waveform of a direct sound and the envelope for resonance sound is attached to a waveform of a resonance sound, which a musical sound corresponding to a state in which the damper pedal is pressed is generated.
Further, an apparatus for generating resonance data of sound signal data is disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2002-311957. The apparatus includes a plurality of delay units coupled in series, provides a resonance coefficient to the respective delay units, and multiplies delayed musical signal data by a delay coefficient to generate the resonance data.
Furthermore, it has been proposed an apparatus that, when a pedal other than a damper pedal is pressed, generates a musical sound containing the pedal effect. For example, Jpn. Pat. Appln. KOKAI Publication No. 05-80749 discloses an apparatus that includes first to third groups of sound sources and a group of not-struck-string sound sources. The sound sources of the first to third groups store sound data of struck strings. The not-struck-string sound sources store sound data of strings which are not struck. When a shift pedal is pressed, the apparatus reads data from the group of not-struck-string sound sources in place of the second and third groups of sound sources and also changes filtering characteristics, thereby generating a musical sound containing a shift pedal effect.
However, the above techniques disclosed in Jpn. Pat. Appln. KOKAI Publication No. 06-149245 and Jpn. Pat. Appln. KOKAI Publication No. 05-80749 need to store a large amount of data to provide sound sources for generating the pedal effect (e.g., for storing waveform data of a resonance sound or sound data of not struck strings).
In the apparatus disclosed in Jpn. Pat. Appln. KOKAI Publication No. 2002-311957 does not require another sound source for a resonance sound because resonance data of a specific resonant frequency is generated based on original sound signal data, and the generated resonance data is attached to the original sound signal data.
Hereinafter a device that produces a resonance sound of one resonant frequency will be referred to as a resonator. In the case where as many resonators as the number of keys or the number of strings including sub-strings are provided, respective resonance intensities can be appropriately controlled in such a manner that respective resonators generate items of resonance data based on resonant frequencies of the respective strings.
However, the number of resonators which can be provided has a limit. Therefore, an intensity of a resonance sound varies depending on a pitch of a musical sound to be generated, and a resonance sound of a specific resonant frequency at a specific pitch is emphasized. As a result, a harsh resonance is generated.